In the leather processing industry, there is a large number of additives, agents, etc., which need to be impregnated into the body of the leather so that they can perform their required function effectively. In the past, such materials have been impregnated into the leather using a number of different processes according to the nature of the additive, agent, etc. The present invention is concerned with providing a general purpose method which is capable of impregnating a wide range of different materials into the leather, but using a generally similar process. Accordingly the present invention contemplates first encapsulating the material or agent into a micro-encapsulated form. Once in this form, the impregnation process may be determined substantially on the basis of the size and composition of the micro-capsule shells rather than exclusively on the basis of the material which is required to be added.
U.S. Pat. No. 4,510,188 describes a method for making a textile or leather material with a chromatic effect in which a layer of a micro-encapsulated liquid cholesteric crystal material is applied to the surface of the textile material or leather. The micro-encapsulated material is applied as a dispersion of capsules in a synthetic resin. In this process, the material is applied as a surfacial layer rather than being impregnated into the fibrous structure of the leather. The present invention differs from the processes disclosed in U.S. Pat. No. 4,510,188 because they require an encapsulated material to be at least partially impregnated into the leather rather than remaining as a surfacial layer
U.S. Pat. No. 5,368,609 discloses a process for softening leather in which thermoexpansible microcapsules (TEMCs) are impregnated into the leather and then caused to expand. The TEMCs contain a volatile liquid which is designed to evaporate and cause the capsule to expand by preferably ten to sixty times their original volume. This technique is concerned with the mechanical function of the microcapsules rather than using the capsules as a vehicle for impregnating material into the leather. The microcapsules are impregnated into the leather in a wet process.
German Published Application DE-A-3921145 discloses an arrangement for rendering leather surfaces matt. In this process a microcapsules material is applied to the surface of the leather by means of a spray gun, to provide a surfacial coating.
WO95/34609 discloses an arrangement in which a binder containing encapsulated phase change materials is coated to a leather substrate. This Specification refers to a surfacial coating rather than a partial or complete impregnation of the leather material.